Interlocking Means for Carton Panels

ABSTRACT

A panel interlocking arrangement for securing together a pair of panels ( 28   b,    28   a ). The two panels may form overlapping panels of a paperboard carton. The interlocking arrangement comprises a locking tab ( 60 ) having a heel ( 60   b ) and a toe ( 60   a ). The locking tab is provided adjacent an end ( 40 ) of one ( 28   b ) of the panels and is hinged about its centre to that panel by a pair of divergent fold lines ( 63, 65 ). The interlocking arrangement further comprises one or more locking apertures ( 70 ) formed in the other ( 28   a ) of the panels. The one or more apertures are shaped in complementary fashion to the locking tab. To lock the panels together, the locking tab is inserted into the one or more apertures. The insertion of the locking tab is facilitated by both the heel and toe of the locking tab being pivotal about the divergent fold lines.

BACKGROUND OF THE INVENTION

This invention relates to panel interlocking means for securing together a pair of panels, for example, adjacent overlapping panels of a paper-board carton. In some situations, these panels are provided by the opposite ends of a wrapper blank which are brought together and interlocked.

Locking tabs which are struck from one end of a carton wrapper and which are arranged to be driven through corresponding apertures, defined by retaining tabs, struck from an opposite end of the wrapper are well known e.g. from U.S. Pat. No. 3,955,748 to Calvert. In US '748 an interlocking means is provided which comprises a locking aperture formed in one end panel and arranged to cooperate with a corresponding locking tab joined to the other end panel, the locking tab comprising an integral locking heel and locking toe, which are arranged to be inserted into the aperture.

A similar interlocking means is disclosed in U.S. Pat. No. 4,577,799 to Oliff. In US '799 a locking tab is also formed integrally with the locking aperture to engage the toe of the locking tab thereby to aid in holding the locking tab in an interlocked relationship with the locking aperture.

A similar interlocking means is disclosed in GB 2 400 345 to Paine. In GB '345 a “heel and toe” locking tab is formed at one end of a wallet and the heel and toe are inserted into separate apertures formed at the other end of the wallet to releasably hold the wallet together. The locking tab disclosed in Paine is not wholly pivotal which can made manipulation of the locking tab into the locking aperture difficult.

The prior art locks are often provided in panels at opposite ends of a wraparound carton and when locked together the panels provide a composite bottom wall of a carton. A locking mechanism for this application is therefore intended only to be locked once to hold the carton in an erected form. If however the carton is required to be opened and reclosed, it is desirable to provide a locking mechanism in an upper or side panel of the carton to facilitate the opening and reclosing of the carton. It is therefore necessary to provide a more durable and efficient lock which can be readily operated by a consumer to open and reclose the carton and whilst providing a secure lock.

The present invention seeks to avoid or at least mitigate these and other problems of the prior art by providing a locking arrangement which is more durable, reusable and easier to operate.

SUMMARY OF INVENTION

According to a first aspect of the invention, there is provided a panel interlocking arrangement of the heel and toe type, for securing together first and second panels of a wraparound carton, the interlocking arrangement comprising a locking tab formed at least in part in said first panel and one or more locking apertures provided in said second panel for receiving the locking tab, the locking tab comprising a locking heel and locking toe characterised in that the locking tab is hinged to the first panel by means of a pair of diverging fold lines extending from the locking heel towards the locking toe, said diverging fold lines predetermine a hinging action between the locking tab and the first panel, to facilitate the insertion of each of the locking toe and heel into said one or more locking apertures thereby to lock the panels together.

Preferably wherein each diverging fold line terminates at free edge of the first. The angle defined between the diverging fold lines may determine the extent the whole locking tab can pivot relative to the first panel.

According to a feature of the invention a single locking aperture may be provided into which both the locking toe and locking heel are inserted. The one or more locking apertures may be provided with at least one pair of slits extending outwardly from one of said one or more locking apertures, which slits further facilitate the insertion of the locking tab into said one or more locking apertures. The locking heel may in part be defined by a substantially semi-circular cut line and in part by arcuate end portions, wherein the arcuate end portions terminate at the divergent fold lines. The one or more locking apertures may have a heel-engaging edge, the heel-engaging edge having a slit extending from each end of the heel engaging edge.

Preferably the arcuate end portions of the locking heel each abut an edge of one of said heel engaging edge slits extending from an upper edge of said one or more locking apertures, when the locking tab is engaged within said one or more locking apertures, to provide a secure lock.

Preferably said one or more locking apertures is in part defined by a toe-engaging edge, said toe-engaging edge having a toe engaging edge slit extending from each end of the toe engaging edge to facilitate the insertion of the locking toe (60 a) within said one or more locking apertures. The locking toe may be shaped such that it has arcuate shoulder portions and wherein side portions of said one or more locking apertures are similarly shaped to promote easy insertion of the locking toe within said one or more locking apertures. The second panel may be provided with a first hinge line, the first hinge line extending between said toe-engaging edge slits to define a first engagement tab between said toe engaging edge slits.

Preferably the first engagement tab can hinge about said first hinge line to facilitate the insertion and removal of the locking heel within said one or more locking apertures. The second panel may be provided with a second hinge line extending between each side edge of the aperture and the engagement tab, the second hinge line defining side engagement tabs which are foldable to encourage the insertion of the locking heel within said one or more locking apertures and which aid the secure engagement of the locking tab within said one or more locking apertures.

Alternatively wherein said one or more locking apertures comprises two locking apertures, one locking aperture for receiving the locking toe and a separate locking aperture for receiving the locking heel.

Preferably the locking heel may be spaced and offset the locking toe.

Additionally two locking apertures are disposed in an off set alignment similar to the off set alignment of the locking toe and heel such that the locking toe and heel can be received and held within said two locking apertures to secure the two panels together.

Preferably the locking heel is spaced diagonally from the locking toe, such that the centre of the locking heel lies on different vertical and horizontal axes relative to the vertical and horizontal axes upon which the centre of the locking toe lies. Additionally the locking tab may comprise a second locking heel and said one or more locking apertures comprise a third locking aperture for receiving said second locking heel.

Preferably the centre of the second locking heel lies on the same horizontal axis as the first locking heel and the second locking heel is spaced diagonally from the locking toe such that the centre of the second locking heel lies on different vertical and horizontal axes to the axes on which the centre of the locking toe lies. Preferably said three locking apertures form a triangular locking aperture arrangement for receiving said first and second locking heels and said locking toe.

Additionally the locking tab may comprise a second locking toe and two additional locking heels and said one or more locking apertures may comprise a second locking aperture for receiving the second locking toe and said one or more locking apertures comprise third and fourth locking apertures for receiving said two additional locking heels, together said one or more locking apertures having a trapezoidal arrangement.

Optionally the or each locking toe projects from a free end edge of the first panel.

BRIEF DESCRIPTION OF THE DRAWINGS

Four exemplary embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 shows the blank of a wraparound carton having two panels to be locked together, one panel having a locking aperture and the other panel having a locking tab, according to a first embodiment of the invention;

FIG. 2 shows the blank of a wraparound carton having two panels to be locked together, one panel having a locking aperture and the other panel having a locking tab according to a second embodiment of the invention;

FIG. 3 shows the blank of a wraparound carton having two panels to be locked together, one panel having a locking aperture and the other panel having a locking tab according to a third embodiment of the invention;

FIG. 4A shows a perspective top, front and side view of a carton erected from the blank of FIG. 1 with the locking tab according to the first embodiment of the invention partly engaged in the locking aperture;

FIG. 4B shows a perspective top, front and side view of the carton of FIG. 4A with the locking tab completely engaged in the locking aperture;

FIG. 4C shows an inside view of the front of the carton of FIG. 4B illustrating the locking tab engaged in the aperture;

FIG. 5 is a front view of the locking tab and aperture of the second embodiment of the invention shown in interlocked relationship;

FIG. 6 is a front view of the locking tab and aperture of the third embodiment of the invention shown in interlocked relationship and

FIG. 7 is a perspective view of the carton of FIG. 4B with containers held within the carton.

FIG. 8 shows the blank of a wraparound carton having a panel interlocking arrangement for locking together two panels, one panel having a locking aperture arrangement and the other panel having a locking tab arrangement according to a fourth embodiment of the invention;

FIG. 8A shows an enlarged view of one end of the blank of the wraparound carton showing the locking tab arrangement;

FIG. 8B shows an enlarged view of the other end of the blank of the wraparound carton showing the locking aperture arrangement;

FIG. 9 shows a first step in the locking of the two panels of the wraparound carton of FIG. 1; and

FIG. 10 shows the composite bottom panel of the wraparound carrier which is formed by locking the two panels together.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a blank 10 for forming a wraparound carton is provided with a pair of panels 28 a and 28 b respectively. Panels 28 a and 28 b are adapted to be interlocked and the blank 10 is formed from paperboard or similar foldable sheet material. The panels 28 a and 28 b are disposed at the opposite ends of one and the same wraparound carton blank 10 which is to be formed into a carton sleeve in which panels 28 a and 28 b then provide lower and upper overlapping side panels of the carton. The panels 28 a and 28 b are interlocked by a panel interlocking arrangement comprising a locking tab 60 and a locking aperture 70.

The carton blank 10 is also provided with a series of main panels hinged together in series, which main panels can be folded around a group of articles, such as beverage or food containers C to form a wraparound carton 30 (as shown in FIG. 7). The main panels include a top panel 20 which is hinged on either side to upper bevelled panels 18 a, 18 b. The main panels also include a second side panel 22 and a bottom panel 24. The bevelled panel 18 a is hinged to the upper side panel 28 b. The bottom panel 24 is hinged on either side to lower bevelled panels 26 a, 26 b and the bevelled panel 26 b is hinged to the lower side panel 28 a. The main panels are hinged in series along fold lines 38 a, 30 a, 40 b, 38 b, 46 a, 44 a, 44 b and 46 b, as illustrated in FIG. 1.

The blank 10 is also provided with a series of upper article receiving apertures 50 formed in the upper bevelled panels 18 a and 18 b. The article receiving apertures 50 are each provided with cuts 52 which extend from a lower edge of the aperture 50 into the adjacent upper and second side panels 28 b, 22. The cuts 52 allow an upper portion of the containers C, wrapped within the carton 30, to protrude slightly to encourage a tight fit of the containers C within the carton 30 and also provide a degree of flexibility which can facilitate the operation of the panel interlocking means i.e. the engagement of the locking tab 60 within the locking aperture 70, when the blank 10 is assembled around an article group and a carton 30 formed. A similar array of article receiving apertures 54 are provided in the bottom panels 24 and lower bevelled panels 26 a, 26 b. Similarly cuts 56 are provided to enable a tight fit of the containers within the wraparound carton 30.

Whereas in the embodiments to be described, the panel interlocking means is illustrated with reference to a wraparound carton, this is to serve as an example only, it being understood that there are a variety of carton structures and arrangements in which the panel interlocking means could be employed, all of which will be obvious to one skilled upon reading the following description. Indeed it will also be obvious that the panel interlocking means herein described can be used for interlocking panels formed of foldable sheet material that may or may not be panels of a carton and also that more than one interlocking means could be employed. The remainder of the description therefore focuses upon the panel interlocking means.

Side panel 28 b includes a locking tab 60 projecting outwardly in the plane of the panel 28 b from an end edge 40 of that panel. The locking tab 60 comprises an integral locking heel 60 b and integral locking toe 60 a. The locking tab 60 is hinged to panel 28 b along fold lines 63 and 65. The fold lines 63, 65 are positioned on either side of the locking tab 60, substantially in the middle of the tab, and diverge from the locking heel 60 b towards the locking toe 60 a. The angle of the fold lines 63, 65 relative to the end edge 40 is, in this embodiment less than 180° so that the fold lines diverge from the locking heel 60 b. The locking heel 60 b is struck from the side panel 28 b and has a leading edge 66. The locking heel 60 b is adjoined to the hinge connections 63, 65 by arcuate portions 68, which arcuate portions 68 are so shaped to improve the engagement of the locking tab within the locking aperture 70. In use the arcuate portions 68 provide a locking edge for cooperation with an edge 72 of the locking aperture 70. The locking toe 60 a has a trailing edge 62 and is shaped in complementary fashion to the locking aperture 70 such that in use shoulder portions 61 of the locking toe 60 a provide a locking edge for cooperation with the edge of slits 77 a, 77 b of the locking aperture 70.

Panel 28 a includes the locking aperture 70 which is formed in complementarily fashion to the shape of the locking tab 60. The locking aperture 70 is defined in part by a lower edge 74, opposite side edges 76 and an upper edge 72 which upper edge 72 cooperates with the arcuate portions 68 of the leading edge 66. The locking aperture is provided with a series of radially or outwardly extending pairs of slits 73 a/73 b, 75 a/75 b and 77 a/77 b. Slits or nicks 73 a, 73 b extend from the upper edge 72 to assist the insertion of the locking toe 60 b into the locking aperture 70. Side slits 77 a, 77 b extend outwardly from the side 76 of the locking aperture 70 and are positioned and angled such that upon insertion of the locking tab 60 into the locking aperture 70, the side slits 77 a, 77 b define edges which may be abutted by the shoulder portions 61 of the locking toe 60 a. Finally, the slits 75 a, 75 b extend from the lower edge 74 and in part define a tab between the slits 75 a, 75 b and the lower edge 74. Which tab is, to some degree, flexible to allow that portion of the lower side panel 28 a immediately beneath the lower edge 74 to move inwardly and outwardly relative to the remainder of the lower side panel 28 a to facilitate the locking an unlocking of the panel interlocking means.

To construct the carton 30 from the blank 10, the main panels are sequentially folded about fold lines 38 a, 30 a, 40 b, 38 b, 46 a, 44 a, 44 b and 46 b and the upper and lower side panels 28 a, 28 b are thereby brought into overlapping relationship. In order to lock together panels 28 b and 28 a, the locking tab 60 is pivoted about the angled or diverging fold lines 63 65. The diverging fold lines 63, 65 provide means for predetermining the hinging action between the locking tab 60 and upper side panel 28 b.

The predetermined hinging action facilitates the pivoting of locking tab 60 such that locking tab 60 is folded substantially perpendicular position relative to the lower side panel 28 a. In this way, the leading edge 66 of the locking toe 60 b can be inserted into the locking aperture 70 by sliding the locking toe 60 b against upper edge 72. The shaped side edges 76 of the locking aperture 70 encourage the locking toe 60 b to engage the upper edge of the aperture 70. This is illustrated in FIG. 4A, wherein the locking toe 60 b is inserted by rotating the locking tab 60 about the fold lines 63, 65 until the locking tab 60 abuts the lower side panel 28 a and the locking heel 60 b can be pushed no further.

The locking heel 60 a is then rotated about fold lines 63, 65 such that the locking toe 60 b abuts an inside face of the lower side panel 28 a. The locking heel 60 a then overlies a lower portion of the locking aperture 70. The locking tab is again rotated about the fold lines 63, 65 but in the opposite direction to the first rotation thereby to accommodate the insertion of the locking heel 60 a.

Again the diverging fold lines 63, 65 facilitate the hinging action or pivotal movement of the locking tab 60 in the reverse direction to facilitate the insertion of the locking heel 60 a. The shoulders 61 of the locking heel 60 a can then be pushed past the side edge 76 of the locking aperture 70, assisted by the slight inward displacement of the portion of the lower side panel 28 a between slits 77 a, 75 a and 77 b, 75 b. The lower edge 62 of the locking heel 60 a is also pushed past the lower edge 74 of the locking aperture. The tab beneath lower edge 74 may displace or give inwardly of the aperture 70 until the locking heel is pushed inside the aperture 70. The natural resilience of the paperboard material causes the tab beneath lower edge 74 and the portion of the lower side panel 28 a, between slits 77 a, 75 a and 77 b, 75 b, to relax into coplanar alignment with the remainder of the lower side panel 28 a.

Furthermore the locking heel 60 a relaxes into an unfolded position and abuts the inside face of the lower side panel 28 a thereby interlocking the two side panels 28 a, 28 b and forming a composite side panel of the carton 30 as shown in FIGS. 4B and 7. A view illustrating the inside face of the interlocked upper and lower side panels 28 b, 28 a is shown in FIG. 4C. In FIG. 4C dotted lines are used to illustrate parts of the interlocking means which are on the outside of the carton and hence cannot actually be seen from the inside view of the carton. It can also be seen from the view in FIG. 4A that the portions of the lower side panel 28 a between the slits 73 a/76 a and 73 b/76 b overlap a central portion of the locking tab 60.

The locking tab 60 is prevented from sliding with respect to the lower side panel 28 a by virtue of the shape of the locking tab 60 and aperture 70 and the arrangement of slits 77 a, 75 a and 77 b, 75 b. The arcuate portions 61 abut the upper edge 72, the arcuate portions 61 and juxtaposed slits 73 a, 73 b are oppositely angled thereby forming a strong and secure engaging edge when the upper and lower side panels 28 b, 28 a are pulled in opposite directions, away from one another. To prevent the upper and lower side panels 28 b, 28 a being pushed towards each other, when the two panels are interlocked, the end edge 40 may abut an edge created by the side slits 77 a,77 b. In this way a durable and secure interlock is formed.

Second, third and fourth embodiments of the present invention are shown in FIGS. 2, and 5, 3 and 6 and 8-10 respectively. Like reference numbers are used to identify panels and features which are similar to those of the first embodiment, albeit the numbers are raised by a factor of 100, 200 and 300 to distinguish between embodiments. Since the subsequent embodiments share similar features to the first embodiment only differences will be described in detail.

In the second embodiment shown in FIG. 2, an exemplary wraparound carton is again used to illustrate how the interlocking means might be used. In this embodiment side slits 77 a, 77 b are replaced by a weakened arcuate arrangement 180 a, 180 b. The weakened lines or nick lines 180 a, 180 b extend between the slits 175 a, 175 b and a substantially central portion of the side edge 176 a, 176 b of the locking aperture 170 thereby defining engaging tabs 182 a, 182 b. The engaging tabs 182 a, 182 b are hinged to the lower side panel 128 a along the weakened lines 180 a and 180 b respectively. The interlocking means is operated substantially in the same way as in the previous embodiment except for the fact that the weakened lines 180 a, 180 b are similarly shaped to the shoulder portions 161 to assist in the engagement of the locking heel 160 a within the aperture 170. This is so because the engagement tabs 182 a, 182 b can more easily be pushed inward of the lower side panel 128 a since they are hinged about the weakened lines 180 a, 180 b. These hinges allow the locking heel 160 a readily to push past the engagement tabs 182 a, 182 b without causing unnecessary wear to the surrounding area of the lower side panel 128 a. Thus a durable and strong interlocking mechanism is provided. FIG. 5 shows a front view of the interlocked panels 128 a and 128 b.

The third embodiment is illustrated in FIGS. 3 and 6. In this embodiment, the locking aperture 270 has side edges 276 a and 276 b which have shoulder portions 277 a and 277 b which are shaped similarly to the shoulder portions 261 of the locking heel 260 a. The similar shaping of the aperture 270 and locking heel 260 a enables the locking tab 260 to be more easily inserted into the aperture 270. Additionally a weakened arcuate line is provided between the slits 275 a and 275 b thereby more clearly defining a tab 281. The weakened line 279 provides a more definite hinge by which the tab 281 can be folded when the locking heel 260 a is inserted and removed from the locking aperture 270 to lock and unlock the panels 228 a, 228 b.

The fourth embodiment of the invention will now be described.

Referring to FIG. 8, a blank 310 for a wraparound carton is provided with first and second bottom panels 328 a and 328 b respectively, which are adapted to be interlocked. The panels 328 a and 328 b are disposed at the opposite ends of one and the same wraparound carton blank 310 which is to be formed into a carton sleeve in which panels 328 a and 328 b then provide overlapping, interlocked bottom panels of the carton.

The carton blank 310 is provided with a series of main panels hinged together in series, which main panels can be folded around a group of articles, such as bottles (B) to form a wraparound carton. The main panels include a top panel 323 which is hinged on either side to upper side panels 322 a, 322 b. The main panels also include lower side panels 320, 324 and lower bevelled panels 318 a and 326 b. The first bottom panel 328 a is hinged to lower bevelled panel 326 b and the bevelled panel 326 b is in turn hinged to the lower side panel 324. The second bottom panel 328 b is hinged to the lower bevelled panel 318 a, which is in turn hinged to the lower side panel 320. The main panels are hinged in series along fold lines 338 a, 340 a, 340 b, 338 b, 346 a, 344 a, 344 b and 346 b, as illustrated in FIG. 8.

The blank 310 is also provided with a series of upper article receiving apertures 350 formed in the upper side panels 322 a and 322 b. These are similar to those of the preceding embodiments and therefore not further described.

Second bottom panel 328 b includes a locking tab arrangement which comprises a pair of integral locking heels 360 b, 360 c and an integral locking toe 360 a. The locking tab arrangement is hinged to panel 328 b along fold lines 363, 365 and 367. The fold lines 363, 365 are positioned on either side of the locking heels 360 b, 360 c respectively and diverge from the locking heels 360 b, 360 c toward an end edge 340 of the second bottom panel 328 b. Fold line 367 extends between the adjacent locking heels 360 b, 360 c. The angle of the fold lines 363, 365 relative to the fold line 367 is, in this embodiment, acute so that the fold lines diverge from the locking heels 360 b, 360 c toward the locking toe 360 a.

The locking heels 360 b, 360 c are struck from the second bottom panel 328 b and are shaped similarly to those of the earlier embodiment. Nevertheless it is envisaged that the locking heels could take a different form, providing that the locking apertures 370 b, 370 c which are formed in the first bottom panel 328 a are complementarily shaped. In use the arcuate portions 368 provide a locking edge for cooperation with edges 382 a and 382 b of the locking apertures 370 b and 370 c. The locking toe 360 a has a trailing edge 362 and is shaped in complementary fashion to a locking aperture 370 c which is also formed in the first bottom panel 328 a. The locking toe 360 a is shaped such that shoulder portions 361 are provided. The shoulder portions 361 are arranged to co-operate with outwardly extending side slits 377 a, 377 b of the locking aperture 370 a.

The first bottom panel 328 a comprises a locking aperture arrangement which includes locking apertures 370 a, 370 b and 370 c, which are each formed and positioned in an arrangement complementarily to the shape of the locking tab arrangement. In this embodiment the locking aperture arrangement is triangular and mimics the orientation of the locking heels 360 b, 360 c and locking toe 360 a.

Turning to the details of the locking aperture arrangement, the locking aperture 370 a is defined in part by a lower edge 374, opposite side edges 376 and an upper edge 372 which upper edge 372 cooperates with the arcuate portions 368 of the leading edge 366 of the locking toe 360 a when the bottom panels 320 a, 320 b are interlocked. The locking aperture 370 a is provided with a radially or outwardly extending pair of slits 377 a/377 b that are positioned and angled such that upon insertion of the locking toe 360 a into the locking aperture 370 a, the side slits 377 a, 377 b define edges which may be abutted by the shoulder portions 361 of the locking toe 360 a. Additionally, slits 375 a, 375 b extend from the lower edge 374 and in part define a tab 378 between the slits 375 a, 375 b and the lower edge 374. The tab 378 is, to some degree, flexible to allow that portion 378 of the first bottom panel 328 a, immediately beneath the lower edge 374, to move inwardly and outwardly relative to the remainder of the first bottom panel 328 a to facilitate the locking and unlocking of the locking toe 360 a within the locking aperture 370 a. The two further apertures 370 b, 370 c struck from the first bottom panel 328 a are each defined by an arcuate edge 384 a, 384 b and a curvilinear edge 382 a, 382 b. Each of the locking apertures 370 b, 370 c is shaped and positioned to be in alignment with a respective locking heel 360 b, 360 c, such that when the blank 310 is formed into a wraparound carrier, each locking heel 360 b, 360 c can be inserted into the corresponding locking aperture 370 b, 370 c.

To construct a carton from the blank 310, the main panels are sequentially folded about fold lines 338 a, 330 a, 340 b, 338 b, 346 a, 344 a, 344 b and 346 b around an assembled group of bottles (B). In this embodiment two bottles are contained within the carrier 330 and the top panel 323 is placed on top of the bottles, the upper side panels and the upper and lower side panels 322 a, 322 b, are folded down the sides of the bottles (B), as are the lower side panels 320, 324. When the side panels 322 a, 322 b 320, 324 are in place, the first and second bottom panels 328 a, 328 b are interlocked to form a composite bottom wall and to complete the construction of the carrier 330.

In order to lock together panels 328 b and 328 a, the locking tab arrangement is pivoted about the fold lines 363, 365 and 367. The locking tab arrangement is folded such that it is substantially perpendicular to the first bottom panel 328 a as illustrated in FIG. 9. From this position, the leading edges 366 of each locking heel 360 b, 360 c, can be inserted into the corresponding locking aperture 370 b, 370 c, by sliding the locking heels 360 b, 360 c against edges 382 a, 382 b.

The locking tab arrangement is then rotated about fold lines 363, 365 and 367 toward the first bottom panel 328 a and into co-planar overlapping relationship. The locking toe 360 a then overlies a lower portion of the locking aperture 370 and the locking heels 360 b, 360 c lie in a co-planar relationship with an underside face of first bottom panel 328 a. The shoulders 361 of the locking toe 360 a can then be pushed past the upper edge 374 of the locking aperture 370 a, assisted by the slight inward displacement of tab 378. The leading edge 362 of the locking toe 360 a is also pushed past the lower edge 374 of the locking aperture 370 a. The tab 378 beneath lower edge 374 may displace or give inwardly of the aperture 370 a until the locking toe 360 a is pushed inside the aperture 370 a. The natural resilience of the paperboard material causes the tab 378 to relax into coplanar alignment with the remainder of the first bottom panel 328 a. Furthermore the locking toe 360 a relaxes into an unfolded position and the shoulder portions 361 abut the inside face of the first bottom panel 328 a thereby interlocking the two bottom panels 328 a, 328 b and forming a composite bottom panel of the carton 330 as shown in FIG. 10.

The locking tab arrangement is prevented from sliding with respect to the lower side panel 328 a by virtue of the shape of the locking toe and heels 360 a, 360 b, 360 c and apertures 370 a, 370 b, 370 c and the arrangement of slits 377 a, 375 a and curvilinear edges 383 a, 385 a. The arcuate portions 368 and curvilinear ends 383 a, 385 a are oppositely angled thereby forming a strong and secure engaging edge when the first and second panels 328 b, 328 a are pulled in opposite directions, away from one another and this engagement serves to lock the panels together. One benefit of utilising an offset locking toe and heel arrangement is that rotation of the first and second bottom panels 328 a, 328 b relative to one another is also restricted.

In this embodiment the locking toe 360 a and locking heels 360 b, 360 c are positioned on the vertices of a notional isosceles triangle. Similarly, the centres of the locking apertures 370 a, 370 b and 370 c define a triangular shape. The centre of locking toe 360 a lies on horizontal and vertical axes spaced and offset from the horizontal and vertical axes spaced and offset from the horizontal and vertical axes upon which the centre of each locking heel 360 b, 360 c lies. In this embodiment the centres of the locking heels 360 b, 360 c lie on the same horizontal access which is parallel to fold line 367.

The diverging fold lines 63, 65 (163, 165, 263, 265, 363, 365) provide a hinge about which the locking tab 60 (160, 260) can pivot. In contrast to prior art mechanisms wherein locking tabs hinge about a straight fold line, by utilising divergent fold lines which extend from the locking heel, toward the locking toe at an angle relative to a notional line normal to the end of the toe (i.e. in line with 367), the pivotal movement of the locking tab in the present invention is more greatly controlled. The hinging action is predetermined by the angle of the divergent fold lines, which can be optimised such that the whole locking tab is permitted to pivot sufficiently out of the plane of said panel to facilitate its insertion into the locking aperture but restricted by the divergent fold lines from folding further i.e. 180° back into coplanar alignment with that panel. The divergent folds effectively introduce a degree of resilience which encourages the locking tab to return to its natural unfolded position, thus introducing a “snapping” effect, where upon inserting the tab into the aperture the heel locks or “snaps” into a locked position behind the panel in which the locking aperture is formed.

It can be appreciated that various changes may be made without departing from the scope of the present invention, for example, the size and shape of the locking tab and locking aperture may be adjusted to accommodate panels of differing size or shape, providing that the lock and aperture are sized in complementary fashion to one another. Other variations may also be made within the scope of the invention. For example the size, shape, position of the fold lines 363, 365 (and 367) may be altered providing that the locking tab can still pivot or rotate about the hinged connection to assist the insertion of the locking tab into the locking aperture. It will also be apparent that the interlocking mechanism of the present invention could be applied to a variety of cartons and its application is not limited to a wraparound carton. It is also clear that the locking aperture and tab could be formed from opposite ends of a unitary blank, or indeed from two separate panels.

It is also envisaged that the locking mechanism of the present invention may contain only one locking heel provided in an offset position relative to the locking toe, the heel and toe to be received in separate apertures. It is also envisaged that for larger carriers or other applications of the panel interlocking means that the locking tab arrangement could comprise more than one locking toe and more than two locking heels. The locking toe to locking heel ratio may or may not be 1:2, for example in a carrier containing a row of 4 bottles, the locking tab arrangement may comprise two locking toes offset and intermediate a series of three locking heels. In this case the locking aperture arrangement would comprise five apertures arranged in a substantially trapezoidal form.

It will also be recognised that as used herein, any reference to hinged connection should not be construed as necessarily referring to a single fold line only; indeed it is envisaged that hinged connection can be formed from one or more of the following, a score line, a frangible line or a fold line without departing from the scope of the invention. 

1. A panel interlocking arrangement for securing together first and second panels of a carton, the interlocking arrangement comprising a locking tab formed at least in part in said first panel and one or more locking apertures provided in said second panel for receiving the locking tab, the locking tab comprising a locking heel and a locking toe, wherein the locking tab is hinged to the first panel by a pair of diverging fold lines extending from the locking heel towards the locking toe whereby hinging action between the locking tab and the first panel is predetermined to facilitate the insertion of each of the locking toe and heel into said one or more locking apertures to lock the panels together.
 2. A panel interlocking arrangement according to claim 1 wherein each of said diverging fold lines terminates at a free edge of the first panel.
 3. (canceled)
 4. A panel interlocking arrangement according to claim 1 wherein said one or more locking apertures comprises a single locking aperture into which both the locking toe and locking heel are inserted.
 5. A panel interlocking arrangement according to claim 1 wherein said one or more locking apertures are provided with at least one pair of slits extending outwardly from said one or more locking apertures so that the insertion of the locking tab into said one or more locking apertures is facilitated.
 6. A panel interlocking arrangement according to claim 1 wherein the locking heel is in part defined by a substantially semi-circular cut line and in part by arcuate end portions, wherein the arcuate end portions terminate at the divergent fold lines respectively.
 7. A panel interlocking arrangement according to claim 6 wherein said one or more locking apertures have a heel-engaging edge, the heel-engaging edge having a slit extending from each end of said heel engaging edge.
 8. A panel interlocking arrangement according to claim 7, wherein the arcuate end portions of the locking heel each abut an edge of a respective one of said heel engaging edge slits when the locking tab is engaged within said one or more locking apertures.
 9. A panel interlocking arrangement according to claim 1 wherein said one or more locking apertures is in part defined by a toe-engaging edge, said toe-engaging edge having a toe engaging edge slit extending from each end of the toe-engaging edge to facilitate the insertion of the locking toe into said one or more locking apertures.
 10. A panel interlocking arrangement according to claim 1 wherein the locking toe is shaped such that the locking toe has arcuate shoulder portions and wherein side portions of said one or more locking apertures are shaped similarly to the shoulder portions respectively to promote easy insertion of the locking toe into said one or more locking apertures.
 11. A panel interlocking arrangement according to claim 9 wherein the second panel is provided with a first hinge line, the first hinge line extending between said toe-engaging edge slits to define a first engagement tab between said toe engaging edge slits.
 12. A panel interlocking arrangement according to claim 11, wherein the first engagement tab is hingedly connected to the second panel along said first hinge line to facilitate the insertion and removal of the locking toe into and from said one or more locking apertures.
 13. A panel interlocking arrangement according to claim 9 wherein the second panel is provided with a side hinge line extending between each side edge of the one or more locking apertures and an adjacent one of the toe engaging edge slits, the side hinge lines defining side engagement tabs which are foldable to encourage the insertion of the locking toe into said one or more locking apertures and which aid the secure engagement of the locking tab within said one or more locking apertures.
 14. A panel interlocking arrangement according to claim 1 wherein said one or more locking apertures comprises two locking apertures for receiving the locking toe and the locking heel respectively.
 15. A panel interlocking arrangement according to claim 14 wherein the locking heel is spaced and offset from the locking toe.
 16. A panel interlocking arrangement according to claim 15 wherein the two locking apertures are disposed in an offset alignment similar to the offset alignment of the locking toe and heel such that the locking toe and heel can be received and held within said two locking apertures to secure the two panels together.
 17. A panel interlocking arrangement according to claim 15 wherein the locking heel is spaced diagonally from the locking toe such that the centre of the locking heel lies on different vertical and horizontal axes relative to the vertical and horizontal axes upon which the centre of the locking toe lies.
 18. A panel interlocking arrangement according to claim 14 wherein the locking tab comprises a second locking heel and said one or more locking apertures comprises a third locking aperture for receiving said second locking heel.
 19. A panel interlocking arrangement according to claim 18 wherein the centre of the second locking heel lies on the same horizontal axis as the first locking heel and wherein the second locking heel is spaced diagonally from the locking toe such that the centre of the second locking heel lies on different vertical and horizontal axes to the axes on which the centre of the locking toe lies. 20-21. (canceled)
 22. A panel interlocking arrangement according claim 1 wherein the locking toe projects from a free end edge of the first panel.
 23. A carton comprising a series of main panels including first and second panels which are secured together by a panel interlocking arrangement, the interlocking arrangement comprising a locking tab formed at least in part in said first panel and one or more locking apertures provided in said second panel for receiving the locking tab, the locking tab comprising a locking heel and a locking toe, wherein the locking tab is hinged to the first panel by a pair of diverging fold lines extending from the locking heel towards the locking toe. 